The online magazine Next City quotes me in an informative story about urban farming.
Dunn admits there aren't enough high-end restaurants or CSA customers willing to pay a premium for the produce generated by 10 or 20 one-acre [urban] farms, much less 10,000. He's looking for alternative buyers, such as hospitals or schools, but has yet to hit on a scalable option.
So-called "vertical farms" have additional problems, but I run into this scaling problem all the time.
When I was at UC Davis, people gushed about how much "more sustainable" a farm that grew seeds of native plants was, relative to those growing wheat, almonds, or tomatoes. Great, but that one farm pretty much saturated the market for native-plant seeds.
My brother earns a reasonable income growing wonderful vegetables and fruits organically, but that doesn't mean it would be easy to convert all our farms to organic methods. If each acre of organic farm needs manure from chickens fed corn from four acres of land fertilized with synthetic fertilizer, that seems to set an upper limit of 25% for organic farmland. Long before that, though, we might run out of customers willing to pay organic premium prices.